The absence of light-dark cycles in space (e.g., on the shuttle or space station) results in disruptions of sleep. It has been proposed that humans who spend prolonged time in space are suffering from jet-lag – the internal desynchronization of clocks in various tissues.
A new experiment on the space station will take a somewhat different strategy than usual. Instead of measuring EEG (brain activity), it will monitor EKG (heart activity) over a period of 150 days.
The idea, brought by Irish researchers, is that EEG monitoring is not capable of measuring internal desynchronization of the myriads of clocks in our body. If the astronauts are indeed jet-lagged, this may not be apparent from the measurement of brain function which presumably follows the timing of the main pacemaker in the suprachiasmatic nucleus. The new approach will also look at the timing of peripheral oscillators to see if they are out of sync with the brain – which would be the true marker of jet-lag.